They just want to be able to identify one another.
"Now, the Star-Belly Sneetches
Had bellies with stars.
The Plain-Belly Sneeches
Had none upon thars.
The stars weren't so big. They were really so small
You might think such a thing wouldn't matter at all.
But, because they had stars, all the Star-Belly Sneetches
Would brag, "We're the best kind of Sneetch on the beaches."
With their snoots in the air, they would sniff and they'd snort
"We'll have nothing to do with the Plain-Belly sort!"
And whenever they met some, when they were out walking,
They'd hike right on past them without even talking."